I`d like to create my own annotations to annotate some local variable. To write the annotation is not the problem, the problem is to get the information of them at the Runti
JLS 9.6.1.2 does indeed state that local variable annotations are not retained. However, JSR 308 is working its way through the community process. It should give you the capability you need.
If you want an interim solution, here is an implementation of JSR 308.